Vertical-cavity surface-emitting laser arrays for miniaturized integrated optical lattice modules

Vertical-cavity surface-emitting lasers (VCSELs) can be readily arranged in two-dimensional arrays for diverse applications such as parallel fiber-optic data transmission or high-power generation for illumination, but also optical trapping in microfluidic channels. Optical trapping is a phenomenon where a focused laser beam attracts particles to the beam center [1]. These forces, which arise from momentum transfer, enable the contamination-free handling of micrometer-sized particles in various applications. So-called optical lattices are two-dimensional arrangements of optical traps and are an attractive tool for automated particle handling, e.g., deflection or sorting. Typical methods for the formation of the beam patterns such as interferometry [2] or holography [3] require the use of bulky external optics which need accurate alignment. By directly integrating VCSEL arrays with microfluidic channels, it is possible to minimize the distance between the lasers and the particles. External optics can thus be eliminated. Owing to the small beam divergence, optical manipulation is then performed without any focusing lenses.